This invention relates to a conveyor positioning structure for loading and conveying machines.
Broadly, such machines utilize a front end gathering implement to sweep rock, sand, ore or other loose material onto a self-contained conveyor for transport to a discharge location, usually disposed at the rear of the machine. An apron is disposed at the forward conveyor end, has a front end edge adapted to move forwardly along the ground with the machine and a rear end portion over which the material moves onto the conveyor. The gathering implement is normally mounted to the front portion of the machine frame, extends substantially ahead of the apron and is adapted to force material up the inclined apron.
Vehicle transport means, such as crawler treads, support the machine on the ground and may be positioned substantially behind the apron and front frame portion to move the center of gravity of the entire device rearwardly in view of the substantial weight forces at the front.
The loading and conveying machines under consideration here can be utilized in tunneling operations, although it is contemplated that they may find more extensive use above ground. In any event, they are often subject to variations in level of terrain, both during actual loading and also during transport from place to place.
In order to accommodate rough terrain, and for transport purposes, it has been found desirable to mount the conveyor on a fixed pivot intermediate its ends and also to pivotally mount the rear of the apron to the machine frame and as low as possible. Pivotal adjustment of these elements had been accomplished by suitable hydraulic cylinders and the like.
It has been found that the gap or clearance space between the rear apron edge and the conveyor should be as narrow as possible. If material rolls backwardly down the inclined conveyor, as sometimes happens, it may tend to enter a gap which is too wide and thereby jam the mechanism.
In some instances, as where the rear apron edge is placed above and slightly forwardly of the conveyor front end, the gap may be so wide that jamming occurs too frequently. On the other hand, too small a gap between the rear apron edge and the conveyor end portion can cause substantial difficulties. Primarily, pivoting of either the conveyor or apron has required careful pivotal adjustment of the other respective element at the same time, lest the two elements collide and damage each other. With the heavy type of machinery involved here, such damage can be extensive and result in undesirably long down times.
The problem can occur when it is desired to lower the rear discharge end of the conveyor to accommodate a dumping receptacle or the like. When the conveyor is mounted on a fixed central pivot, the front conveyor end will be raised and will collide with the rear apron edge unless the apron has been pivoted upwardly. Such re-positioning of the apron may be undesirable because the front apron edge may then no longer rest on the ground. The problem can also arise when the front edge of an apron floating on the ground suddenly drops into a ground depression, causing the rear apron edge to drop and collide with the conveyor, unless the front end of the conveyor has been lowered.